To fill a content medium, such as a juice beverage and tea, into a synthetic resin (e.g., polyethylene terephthalate) bottle, it has been customary to employ a so-called hot filling method of filling the content medium at a temperature of, for example, approximately 90° into the bottle, immediately followed by sealing the bottle with a cap, for sterilization of the contents and the bottle. Since the hot filling method involves cooling of the bottle after sealed, the inside of the bottle is brought to a significant reduced pressure state, and measures, such as providing the trunk with an area (so-called a reduced pressure absorbing panel) that is easily deformable or by allowing the bottom to be displaced toward the inside direction of the bottle (e.g., refer to Patent Literature 1), are taken to prevent the appearance of the bottle from undergoing unsightly deformation. Imparting the bottom with a reduced pressure absorption function as in Patent Literature 1 provides the following advantages. That is to say, design flexibility is enhanced because there is no need to provide the reduced pressure absorbing panel in the trunk, which attracts attention as the bottle appearance. Moreover, since there is no need for such a deformable reduced pressure absorbing panel, the trunk maintains its surface rigidity and has good shape retainability.